Method and Wearable Electronic Device for Imbalance Warning

1. A method for imbalance warning to be implemented by a wearable electronic device positioned on a body part of a user, the wearable electronic device including an inertial measurement unit (IMU), an output unit and a processing unit electrically connected to the IMU and the output unit, the IMU including a three-axis accelerometer, the method comprising steps of: by the IMU, obtaining acceleration data related to the wearable electronic device during a calibration period, in which the user continuously takes a plurality of steps walking on the ground while maintaining balance, wherein the acceleration data include first acceleration values in a first direction, second acceleration values in a second direction that is perpendicular to the first direction, and third acceleration values in a third direction that is perpendicular to the first and second directions, the first direction relating to an anteroposterior axis of the user; by the processing unit, obtaining an angle threshold that is associated with the user and that is related to sway of the body part of the user based on the acceleration data thus obtained through sub-steps of: determining a plurality of step durations that correspond respectively to the steps; for each of the step durations, calculating a step length value of the step based on the first and second acceleration values that are measured during the step duration, calculating a displacement value based on the third acceleration values that are measured during the step duration, the displacement value relating to displacement of the body part in the third direction, and calculating a reference sway angle as cot −1 (L1/L2), where L1 represents the step length value and L2 represents the displacement value; and calculating the angle threshold as an average value of the reference sway angles calculated respectively for the step durations; by the IMU, obtaining angular velocity data of the wearable electronic device during a unit of time; by the processing unit, calculating a sway angle of the body part with respect to the unit of time based on the angular velocity data measured during the unit of time; by the processing unit, determining whether the sway angle thus calculated exceeds the angle threshold; and by the processing unit, when it is determined that the sway angle exceeds the angle threshold, controlling the output unit to output a first signal that indicates imbalance of the user.

2. The method of claim 1 , further comprising a step of: by the processing unit, when it is determined that the sway angle does not exceed the angle threshold, controlling the output unit to output a second signal that indicates balance of the user.

3. The method of claim 1 , wherein the sub-step of determining a plurality of step durations includes sub-steps of: determining a plurality of troughs of a waveform that is composed of the third acceleration values which are measured during the calibration period; and determining the step durations respectively as plural time durations each between two time points corresponding respectively to adjacent two of the troughs.

4. The method of claim 1 , the IMU further including a multi-axis gyroscope that has a sampling period equal to a length of the unit of time, wherein: the step of obtaining angular velocity data includes measuring, during the unit of time, a first angular velocity about a first axis extending in the first direction, and a second angular velocity about a second axis extending in the second direction; and the step of calculating a sway angle is to calculate the sway angle that relates to sway with reference to the anteroposterior axis of the user during the unit of time.

5. The method of claim 1 , wherein the step of controlling the output unit to output a first signal is to control the output unit to output the first signal that includes at least one of a visual signal or an audio signal.

6. A method for imbalance warning to be implemented by a wearable electronic device positioned on a body part of a user, the wearable electronic device including an inertial measurement unit (IMU), an output unit and a processing unit electrically connected to the IMU and the output unit, the IMU including a three-axis accelerometer, the method comprising steps of: by the IMU, obtaining acceleration data related to the wearable electronic device during a calibration period, in which the user continuously takes a plurality of steps walking on the ground, wherein the acceleration data include first acceleration values in a first direction, second acceleration values in a second direction that is perpendicular to the first direction, and third acceleration values in a third direction that is perpendicular to the first and second directions, the first direction relating to an anteroposterior axis of the user; by the processing unit, obtaining an angle threshold based on the acceleration data thus obtained through sub-steps of: determining a plurality of troughs of a waveform that is composed of the third acceleration values that are measured during the calibration period; determining plural step durations respectively as plural time durations each between two time points corresponding respectively to adjacent two of the troughs; for each of the step durations, calculating a step length value of the step based on the first and second acceleration values that are measured during the step duration, calculating a displacement value based on the third acceleration values that are measured during the step duration, the displacement value relating to displacement of the body part in the third direction, and calculating a reference sway angle as cot −1 (L1/L2), where L1 represents the step length value and L2 represents the displacement value; and calculating the angle threshold as an average value of the reference sway angles calculated respectively for the step durations; by the IMU, obtaining angular velocity data of the wearable electronic device during a unit of time; by the processing unit, calculating a sway angle of the body part with respect to the unit of time based on the angular velocity data measured during the unit of time; by the processing unit, determining whether the sway angle thus calculated exceeds an angle threshold that is associated with the user and that is related to sway of the body part of the user when walking a plurality of steps while maintaining balance; and by the processing unit, when it is determined that the sway angle exceeds the angle threshold, controlling the output unit to output a first signal that indicates imbalance of the user.

7. The method of claim 6 , the IMU further including a multi-axis gyroscope that has a sampling period equal to a length of the unit of time, wherein: the step of obtaining angular velocity data includes measuring, during the unit of time, a first angular velocity about a first axis extending in the first direction, and a second angular velocity about a second axis extending in the second direction; and the step of calculating a sway angle is to calculate the sway angle that relates to sway with reference to the anteroposterior axis of the user during the unit of time.

8. The method of claim 7 , wherein the step of calculating a sway angle includes: combining the first angular velocity and the second angular velocity to obtain a resultant angular velocity; and calculating the sway angle by integrating the resultant angular velocity over the unit of time.

9. A wearable electronic device for warning a user of imbalance, comprising: a main body configured to be fastened to a body part of the user in a manner that said main body moves synchronously with the body part of the user; an inertial measurement unit (IMU) attached to said main body and configured to obtain acceleration data and angular velocity data of said main body, the IMU including: a three-axis accelerometer configured to obtain the acceleration data that include first acceleration values in a first direction, second acceleration values in a second direction that is perpendicular to the first direction, and third acceleration values in a third direction that is perpendicular to the first and second directions, the first direction relating to an anteroposterior axis of the user; and a multi-axis gyroscope configured to obtain the angular velocity data that include a first angular velocity about a first axis extending in the first direction, and a second angular velocity about a second axis extending in the second direction; a processing unit attached to said main body and electrically connected to said IMU; and an output unit attached to said main body, and electrically connected to and controlled by said processing unit, wherein, when said wearable electronic device is operating in a calibration mode, said IMU is configured to obtain the acceleration data during a calibration period, in which the user continuously takes a plurality of steps walking on the ground while maintaining balance, and to send the acceleration data thus obtained to said processing unit, and said processing unit is configured to obtain an angle threshold that is related to sway of the body part of the user based on the acceleration data received from said IMU by determining a plurality of step durations that correspond respectively to the steps; for each of the step durations, calculating a step length value of the step based on the first and second acceleration values that are measured during the step duration, calculating a displacement value based on the third acceleration values that are measured during the step duration, the displacement value relating to displacement of the body part in the third direction, and calculating a reference sway angle as cot −1 (L1/L2), where L1 represents the step length value and L2 represents the displacement value; and calculating the angle threshold as an average value of the reference sway angles calculated respectively for the step durations, wherein, when said wearable electronic device is operating in a monitoring mode, said IMU is configured to obtain the angular velocity data during a unit of time and to send the angular velocity data thus obtained to said processing unit, and said processing unit is configured to calculate a sway angle of the body part with respect to the unit of time based on the angular velocity data measured during the unit of time, to determine whether the sway angle thus calculated exceeds the angle threshold, and to control said output unit to output a first signal that indicates imbalance of the user when it is determined that the sway angle exceeds the angle threshold.

10. The wearable electronic device of claim 9 , wherein said processing unit is further configured to, when said wearable electronic device is operating in the monitoring mode, control said output unit to output a second signal that indicates balance of the user when it is determined that the sway angle does not exceed the angle threshold.

11. The wearable electronic device of claim 9 , wherein said processing unit is configured to determine a plurality of troughs of a waveform that is composed of the third acceleration values that are measured during the calibration period; and determine the step durations respectively as plural time durations each between two time points corresponding respectively to adjacent two of the troughs.

12. The wearable electronic device of claim 9 , wherein said multi-axis gyroscope has a sampling period equal to a length of the unit of time, and the sway angle of the body part calculated by said processing unit relates to sway with reference to the anteroposterior axis of the user.

13. The wearable electronic device of claim 9 , wherein the first signal outputted by said output unit includes at least one of a visual signal or an audio signal.